1. Field of the Invention
The present invention relates to an actuator drive control device for an active vibration isolation support system, including an elastic body receiving a load of a vibrating body, a liquid chamber in which the elastic body forms at least a part of a wall surface, a movable member changing a capacity of the liquid chamber by reciprocating periodically, and an actuator operating periodically by receiving supply of an electrical current corresponding to a vibration state of the vibrating body.
2. Description of the Related Art
Such an active vibration isolation support system is known from Japanese Patent Application Laid-open No. 7-42783.
This active vibration isolation support system changes a spring constant by applying electrical current to an actuator so as to vibrate a movable member. The relationship between the phase and peak electrical current value of the applied electrical current that sets the spring constant is stored as a map in advance, and the phase and the peak electrical current value of the electrical current to be applied to the actuator are obtained from the map according to the rotational speed of the engine, thereby allowing the active vibration isolation support system to exhibit an effective vibration isolation function in various regions of the rotational speed of the engine.
The inventor has already proposed, in Japanese Patent Application No. 2002-194507, the active vibration isolation support system which gradually decreases a duty ratio of the electrical current which is applied to the actuator from 100% to 0% in a duty group corresponding to one period of vibration, thereby controlling a lift amount of the movable member to be a sine wave form close to a vibration waveform of the engine.
In the active vibration isolation support system that is proposed in the above-described Japanese Patent Application No. 2002-194507, a terminal end portion of a duty group and a start end portion of the next duty group sometimes overlap each other when an engine rotational speed changes in the increasing direction, as will be described in detail below in an embodiment of the present invention. When the two adjacent duty groups overlap each other, the electrical current value supplied to the actuator rises abnormally, leading to problems that the active vibration isolation support system cannot exhibit an effective vibration isolation function and generates noise and the coil of the actuator abnormally generates heat.
The present invention has been achieved in view of the aforementioned circumstances, and an object of the present invention is to prevent impairment of the vibration isolation function of the active vibration isolation support system due to variation in the frequency of an input vibration.